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At least 1,693 records · Page 94
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Dynamic computational optical fringe mitigation in tunable laser absorption spectroscopy

In optical spectroscopic systems where unwanted optical scattering cannot be eliminated, Fabry-Pérot etalons cause unpredictable changes in the spectral background. Frequent system calibration is then required to maintain the desired measurement accuracy, which presents a major limitation to the spectrometer. We introduce a computational approach to mitigate the adverse effects of optical fringing without hardware modifications. Motivated by experimental observations of complicated fringe behaviors, we simplify the problem by decomposing the fringe background into component etalons that can be addressed according to their individual characteristics. The effectiveness of the proposed method is demonstrated on a silicon photonic methane sensor, where accurate measurements of methane concentration are obtained from spectral data strongly affected by optical fringes.

Teng, Chu C. (ORCID:0000000152744835)↗
DOE OSTI2021

Lasing in 15 atm CO 2 cell optically pumped by a Fe:ZnSe laser

10 µm lasing is studied in a compact CO 2 -He cell pressurized up to 15 atm when optically pumped by a ∼50 mJ Fe:ZnSe laser tunable around 4.3 µm. The optimal pump wavelength and partial pressure of CO 2 for generating 10 µm pulses are found to be ∼4.4 µm and 0.75 atm, respectively. Without cavity optimization, the optical-to-optical conversion efficiency reached ∼10% at a total pressure of 7 atm. The gain lifetime is measured to be ∼1 µs at pressures above 10 atm, indicating the feasibility of using high-pressure optically pumped CO 2 for the efficient amplification of picosecond 10 µm pulses.

Tovey, Dana↗
DOE OSTI2022

High-speed silicon microresonator modulators with high optical modulation amplitude (OMA) at input powers >10 mW

A high-speed silicon photonic microdisc modulator is used with more than 10 mW optical power in the bus waveguide, extending the optical power handling regime used with compact silicon resonant modulators at 1550 nm. We present an experimental study of the wavelength tuning range and biasing path required to shift the resonant frequency to the optimal point versus on chip power. We measure the optical modulation amplitude (OMA) along different biasing trajectories of the microdisc under active modulation and demonstrate an OMA of 4.1 mW with 13.5 mW optical power in the bus waveguide at 20 Gbit/s non-return to zero (NRZ) data modulation.

Wang, Xiaoxi↗
DOE OSTI2024

Four-channel optically pumped magnetometer for a magnetoencephalography sensor array

We present a novel four-channel optically pumped magnetometer (OPM) for magnetoencephalography that utilizes a two-color pump/probe scheme on a single optical axis. We characterize its performance across 18 built sensor modules. The new sensor implements several improvements over our previously developed sensor including lower vapor-cell operating temperature, improved probe-light detection optics, and reduced optical power requirements. The sensor also has new electromagnetic field coils on the sensor head which are designed using stream-function-based current optimization. We detail the coil design methodology and present experimental characterization of the coil performance. The magnetic sensitivity of the sensor is on average 12.3 fT/rt-Hz across the 18 modules while the average gradiometrically inferred sensitivity is about 6.0 fT/rt-Hz. The sensor 3-dB bandwidth is 100 Hz on average. The on-sensor coil performance is in good agreement with the simulations.

Iivanainen, Joonas (ORCID:0000000160344604)↗
DOE OSTI2025

CUDO: closed-form universal dwell-time optimization for computer-controlled optical surfacing

Precision optical figuring demands fast and accurate dwell time optimization to reach nanometer- and sub-nanometer-level accuracy in next-generation optical systems. We introduce CUDO (closed-form universal dwell-time optimization), the first, to the best of our knowledge, unified closed-form analytical framework that supports both function-form and matrix-form dwell time models in computer-controlled optical surfacing (CCOS). In contrast to traditional methods, which rely on iterative optimization and hyperparameter tuning, our framework derives direct analytical solutions with no adjustable parameters. This approach unifies the solution principles of existing methods within a single mathematical model, delivering three key advantages: (1) accuracy on par with, or superior to, iterative solvers, (2) substantial reduction in computation time, and (3) numerical robustness. Comparative studies with prior art confirm that closed-form solutions achieve equivalent residual error while removing runtime bottlenecks. By simplifying the implementation and enabling real-time, scalable deployment, CUDO establishes a practical foundation for future deterministic fabrication of large-aperture and high-performance optics.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Fundamental mode excitation via Joule–Thomson light expansion in nonlinear optical lattices

Under linear conditions, power injected from a single waveguide into a multi-core fiber array results in multimode propagation, progressively diminishing the spatial coherence of light. In this work, we introduce a comprehensive approach to mitigate this coherence loss by means of a nonlinear thermodynamic Joule–Thomson expansion. By leveraging the tools of optical thermodynamics, we demonstrate that as light undergoes a sudden transition from a small to a larger nonlinear optical array, it can abruptly drop its optical temperature to near-zero values. During this cooling process, light irreversibly flows into the system's fundamental mode with very high efficiency, synchronizing all elements of the lattice with the input port. We show that this nonlinear effect is highly predictable even in systems of arbitrary geometry and shape and can be controlled precisely by the initial conditions at the input of the array. In particular, for a single injection point, the reduction in optical temperature can be directly determined by the total power, irrespective of the input location.

Pyrialakos, Georgios G. (ORCID:0000000286129694)↗
DOE OSTI2023

Quantum optical memory for entanglement distribution

Optical photons are powerful carriers of quantum information, which can be delivered in free space by satellites or in fibers on the ground over long distances. Entanglement of quantum states over long distances can empower quantum computing, quantum communications, and quantum sensing. Quantum optical memories are devices designed to store quantum information in the form of stationary excitations, such as atomic coherence, and are capable of coherently mapping these excitations to flying qubits. Quantum memories can effectively store and manipulate quantum states, making them indispensable elements in future long-distance quantum networks. Over the past two decades, quantum optical memories with high fidelities, high efficiencies, long storage times, and promising multiplexing capabilities have been developed, especially at the single-photon level. In this review, we introduce the working principles of commonly used quantum memory protocols and summarize the recent advances in quantum memory demonstrations. We also offer a vision for future quantum optical memory devices that may enable entanglement distribution over long distances.

Lei, Yisheng↗
DOE OSTI2025

Electro-optic sampling of classical and quantum light

Full characterization of electric-field waveforms in amplitude and phase is achieved across the terahertz to visible spectral range through interaction with an optical pulse shorter than a half-cycle period via the Pockels (linear electro-optic) effect. This technique of electro-optic sampling has become an indispensable tool in various areas, including ultrafast pump-probe, time-domain and frequency-comb spectroscopies, quantum optics, high-harmonic generation, and attosecond science, and holds great promise for further advances. Not only does it enable spectroscopic measurements with record dynamic range and temporal resolution, along with massively parallel real-time spectral data acquisition, but its remarkable sensitivity also allows the detection of vacuum fluctuations, i.e., “zero-point motion” of electric fields, profoundly impacting our understanding of the fundamental laws of nature.

Benea-Chelmus, Ileana-Cristina (ORCID:000000024814↗
DOE OSTI2021

Anomalous ultrafast all-optical Hall effect in gapped graphene

We propose an ultrafast all-optical anomalous Hall effect in two-dimensional (2D) semiconductors of hexagonal symmetry such as gapped graphene (GG), transition metal dichalcogenides (TMDCs), and hexagonal boron nitride (h-BN). To induce such an effect, the material is subjected to a sequence of two strong-field single-optical-cycle pulses: A chiral pump pulse followed within a few femtoseconds by a probe pulse linearly polarized in the armchair direction of the 2D lattice. Due to the effect of topological resonance, the first (pump) pulse induces a large chirality (valley polarization) in the system, while the second pulse generates a femtosecond pulse of the anomalous Hall current. The proposed effect is fundamentally the fastest all-optical anomalous Hall effect possible in nature. It can be applied to ultrafast all-optical storage and processing of information, both classical and quantum.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Ultrafast optical modulation of vibrational strong coupling in ReCl(CO) 3 (2,2-bipyridine)

Polaritons – hybrid light-matter states formed from the strong coupling of a bright molecular transition with a confined photonic mode – may offer new opportunities for optical control of molecular behavior. Vibrational strong coupling (VSC) has been reported to impact ground-state chemical reactivity, but its influence on electronic excited-state dynamics remains unexplored. Here, we take a first step towards excited-state VSC by demonstrating optical modulation of the ReCl(CO) 3 (bpy), (bpy = 2,2-bipyridine) complex under VSC using femtosecond ultraviolet (UV)-pump/infrared (IR)-probe spectroscopy. We establish ground-state VSC of ReCl(CO) 3 (bpy) in a microfluidic Fabry-Pérot cavity equipped with indium tin oxide (ITO)-coated mirrors. ITO is effectively dichroic as it is reflective in the IR and transmissive in the UV-visible and therefore minimizes optical interference. Excitation with UV pump light drives ReCl(CO) 3 (bpy) into a manifold of electronic excited states that subsequently undergo non-radiative relaxation dynamics. We probe the transient response of the strongly-coupled system in the mid-IR, observing both Rabi contraction and cavity-filtered excited-state absorption signatures. We reconstruct the intrinsic response of intracavity molecules from the transient cavity transmission spectra to enable quantitative comparison with extracavity control experiments. We report no changes in the excited-state dynamics of ReCl(CO) 3 (bpy) under ground-state VSC. However, we do observe significant amplification of transient vibrational signals due to classical cavity-enhanced optical effects. This effort lays the groundwork to pursue direct excited-state VSC aimed at modulating photochemical reactivity.

cavity-enhanced spectroscopy↗
DOE OSTI2023

Optical modeling of a radioisotope atmospheric chamber

Abstract Volatile radioisotopes represent a substantial health risk when released into the environment. To better understand the environmental fate of radioisotopes, the authors constructed a cylindrical steel-walled chamber to simulate the atmospheric processing of volatile radioactive gases. Optical modeling was performed for the properties of simulated sunlight in the chamber to better characterize atmospheric reaction studies. Optical simulations were performed using two wall materials (steel and thin-film silica) and validated against experimental measurements. This optical analysis methodology can be used to improve the fidelity of atmospheric models by accounting for optical inhomogeneities enabling a firmer grasp of radioisotopes’ environmental fate. Graphical abstract

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2023

Temperature Control of Crystal Optics for Ultrahigh-Resolution Applications

The temperature control of crystal optics is critical for ultrahigh resolution applications such as those used in meV-resolved Inelastic Scattering. Due to the low count rate and long acquisition time of these experiments, for 1-meV energy resolution, the absolute temperature stability of the crystal optics must be maintained below 4 mK to ensure the required stability of lattice constant, thereby ensuring the energy stability of the optics. Furthermore, the temperature control with sub-mK precision enables setting the absolute temperature of individual crystal, making it possible to align the reflection energy of each crystal’s rocking curve in sub-meV resolution thereby maximizing the combined efficiency of the crystal optics. In this contribution, we report the details of an EPICS control system using PT1000 sensors, Keithley 3706A 7.5 digits sensor scanner, and Wiener MPOD LV power supply for the analyzer crystals of the Inelastic X-ray Scattering (IXS) beamline 10-ID at NSLS-II**. We were able to achieve absolute temperature stability below 1 mK and sub-meV energy alignment for several asymmetrically cut analyzer crystals. The EPICS ePID record was used for the control of the power supplies based on the PT1000 sensor input that was read with 7.5 digits accuracy from the Keithley 3706A scanner. The system enhances the performance of the meV-resolved IXS spectrometer with currently a 1.4 meV total energy resolution and unprecedented spectral sharpness for studies of atomic dynamics in a broad range of materials.

Gofron, Kaz↗
DOE OSTI2026

Design of an optical amplifier for amplified OSC in IOTA facility at Fermilab

Optical stochastic cooling (OSC) is a cutting-edge beam cooling technology to reduce, control the 3 dimensional spread and the motion of particle beams. It has recently been successfully, experimentally, demonstrated in Fermilab's IOTA storage ring, marking a major step forward in beam cooling. OSC has the potential to significantly improve both the performance and flexibility as a beam cooling system. One promising way to boost OSC performance is by adding a high-gain optical amplifier. However, this amplifier must be carefully designed to meet the specific constraints of the OSC system. A major challenge lies in the limited optical delay, which is just 6 mm for the case of IOTA, set by the beam bypass, restricts us to use a short-length gain medium. This, along with IOTA’s high repetition rate and the relatively long duration of the optical pulses, limits the peak power available for the pump laser without damaging the crystal, which is crucial for achieving strong nonlinear gain. Additionally, it's essential to preserve the phase coherence of the undulator radiation during amplification, which further complicates the amplifier design. This report details a specialized amplifier setup that addresses these challenges, includes simulations of the integrated system, and summarizes the latest experimental progress and results.

Mondal, Abhishek [Fermilab]↗
DOE OSTI2020

The Dark Energy Spectrographic Instrument (DESI) Optical Fiber System

The specific research of the DESI project is to study in detail the expansion history of the Universe over the past 10 billion years. In order to do this, the project designed, fabricated, tested and commissioned the DESI instrument which has been deployed at the Mayall Telescope at the Kitt Peak National Observatory near Tucson, Arizona. The DESI project was conducted by approximately 30 US and foreign national laboratories. The complete instrument includes a prime focus corrector assembly, a focal plane with 5,000 optical fibers whose position can be set by robotic positioners, and ten spectrographs. Each spectrograph can accommodate the light from 500 fibers and include three color channels that are illuminated by a common collimator mirror and other planar transfer optics. In order for this entire system to work, optical fibers are required to connect each positioner to the spectrographs. Our CRADA with Durham University in the UK provided the 10 crucial fiber cables required to connect the DESI focal plane to the 10 spectrographs. The key major goals of this CRADA were achieved. Survey planning was another key component to the Durham contribution. Drs. Frenk, Baugh, Cole, Edge, Lacey, Li, Lucey, Massey, Metcalfe, Norberg and Shanks were all important contributors to the working groups to which they were assigned. Their work to implement emission lines and QSO in lightcone mocks, mocks for non-standard cosmologies/modified gravity, optimization of completeness of BGS in crowded regions and extended source photometry have been vital in the early planning for targets during commissioning. The major role in the project involved Dr. Ray Sharples and his team. They provided a significant portion of the design, fabrication and testing of the optical fiber system. In particular, they were responsible for the design, production of engineering drawings, component procurements, and fabrication of the 10 DESI Science fiber cables. Working in close collaboration with Dr. Claire Poppett, they also designed and fabricated the slit assemblies, the specialized termination of the groups of 500 fibers which plug into the spectrographs.

47 OTHER INSTRUMENTATION↗
DOE OSTI2021

Nonlinear X-ray Optics

Novel X-ray free-electron lasers (XFELs) are capable of producing radiation with unprecedented properties. Specifically, their ultrashort coherent X-ray pulses can generate extreme peak intensities where ordinary rules of light-matter interaction may no longer apply, and nonlinear processes start to become important. XFELs have made it possible to observe some of the most important coherent non-sequential nonlinearities, including X-ray-optical sum frequency generation (SFG), X-ray second harmonic generation (XSHG), two-photon absorption (TPA) and nonlinear two-photon Compton scattering (2PCS). In particular, the 2PCS experiment has led to unexpected results, namely the observation of a substantial anomalous red shift in the energy of photons generated by nonlinear two-photon X-ray Compton scattering in beryllium. The energy shift is in addition to the predicted nonlinear Compton shift and was neither expected from extrapolations from linear X-ray interactions nor from nonlinear effects at optical wavelengths. Our results suggest a novel nonlinear scattering mechanism that can only be observed at high fields at X-ray wavelengths, where the photon energy is a significant fraction of the electron rest mass (and thus a significant momentum transfer to the electron occurs during the scattering) and where the interaction is not dominated by the quiver motion of the electron in the field (ponderomotive potential) as is usually the case at longer (optical) wavelengths. The goal of this research project was the investigation of fundamental nonlinear X-ray-matter interactions. As these processes are typically weak, part of this research is the exploration of more efficient nonlinear X-ray processes by studying novel mechanisms including solid-state effects, the assistance of optical radiation and novel phase-matching techniques. These experiments require extremely large X-ray field strengths, such as produced by XFELs. Nonlinear X-ray effects can lead to important applications in many research fields. For example, it could lead to instantaneous plasma diagnostics for materials in extreme conditions, as a method for combining atomic-scale structural sensitivity with chemical specificity, or as a probe of electron dynamics in solids on the attosecond (1 as = 10 -18 s) time- and Ångstrom (10 -10 m) length scales. In addition, a detailed understanding of nonlinear X-ray matter interactions is crucial for understanding and extending the limits of structural determination at high intensity such as in serial femto-crystallography. The results could have a profound impact on advanced XFEL light sources such as the LCLS-II.

47 OTHER INSTRUMENTATION↗
DOE OSTI2021

Nonlinear Optics Measurements in IOTA

Nonlinear integrable optics is a recently proposed accelerator lattice design approach which allows to generate an amplitude dependent tune shift which is needed in high brightness accelerators to mitigate fast coherent instabilities. Whereas usually octupoles are used to achieve this task, this concept allows doing so without exciting any resonances, in turn preventing any particle loss. The concept is based around a special magnet design, together with specific constraints on the optics of the accelerator. To study such a system, the Integrable Optics Test Accelerator (IOTA) was recently constructed and commissioned at Fermilab. For the assessment of the performance of this concept, good knowledge of the optics and the (non-)linear dynamics without the special magnet is of key importance. As such, measurements were conducted in the IOTA ring, using the captured turn-by-turn data by the beam position monitors after excitation to infer quantities such as amplitude detuning and resonance driving terms. In this note, first results of these measurements are presented.

43 PARTICLE ACCELERATORS↗
DOE OSTI2021

Improved temperature control for measuring the humidity dependence of aerosol optical properties

Aerosols impact climate and cloud formation by their ability to take up water, which leads to changes in their optical properties. To better characterize the interactions of aerosol with water vapor, a humidification section has been added to the Cavity Attenuation Phase-shift Spectrometry (CAPS) instrument. The CAPS is a diode based method that provides simultaneous measurements of both aerosol total optical extinction and scattering in real-time. We are improving the humidity controlled sample line with new temperature controls. The current system suffers from particlelosses and poorly controlled humidity profiles, both of which were corrected for in the systems redesign. This improved wet-CAPS system has been integrated with a dry-CAPS to simultaneously measure the wet and dry aerosol optical properties. The two CAPS monitors were operated in a dry collection mode to ensure there were no biases between the instruments. Initial calibrations and data were collected to test the functionality of the dual CAPS system (wet + dry). The new two channel CAPS system improves our ability to measure the effects of humidity on aerosol optical properties.

58 GEOSCIENCES↗
DOE OSTI2023

Probing Nanocrystal Optical Properties in the Limit of Single Nanocrystals

The Bawendi lab has been at the forefront of the synthesis and characterization of the fundamental photo-physics of quantum confined systems for the past three decades. During this DoE project, our progress has been enabled by both our expertise in single nanocrystal (NC) photoluminescence (PL) spectroscopy as well as our extensive knowledge of the synthetic optimization of various NC semiconductors - all of this forming an efficient feedback loop between characterization and synthesis. Our research in this project has focused on the development and application of novel single emitter optical tools for the characterization of colloidal quantum dots (CQDs) which are semiconducting NCs with size-tunable quantum confined electronic structure. CQDs have had a significant commercial impact as display technologies. They are also commercially available as fluorescent biological markers. CQDs are being investigated as a potential material for photovoltaic or optical sensing applications and as emerging optical quantum materials. We have focused on the fundamental understanding of the optical properties of NCs through the development of novel spectroscopic methods at the single emitter level, including understanding how synthetic and environmental heterogeneities influence NC properties. A major advance in our research has been the development of novel photon resolved correlation spectroscopies that allow us to extract the physics of photo-excited single NCs with unprecedented time and spectral resolution from the photon stream of individual NCs.

36 MATERIALS SCIENCE↗